"Through this collaboration, we are designing, developing and testing a technology for tracking miners trapped inside a collapsed underground mine, using a scenario that assumes that the injured, missing miners are not able to send distress calls," says Professor Fred Cawood, Director of the Wits Mining Institute.

Mining today and in future involves penetrating deep into the Earth and encountering extremely harsh environments. This requires innovative techniques to ensure the health and safety of miners. A challenge of particular interest to researchers is to track trapped miners when a part of the mine has collapsed.

"Most of the currently employed communication technologies would fail in this scenario, leaving rescuers with the impossible task of finding the trapped miners when it is not possible to communicate with them," says Dr Asad Mahmood, senior lecturer in the Wits School of Electrical and Information Engineering, whose research interests include signal processing for communications, hyperspectral imaging, and wireless sensor networks (WSN).

Idrees Zaman, a visiting researcher to Wits and a PhD candidate from the University of Bremen, whose doctorate focuses on wireless sensor networks in agriculture, says: "Wireless sensor networks, which combine through-the-rock, through-broken-earth, and through-the-air communication, have the potential to re-establish the communication link even in a disaster scenario."

Simulating safety through sensors

As a proof-of-concept, a collapse scenario was created inside the mock mine constructed in the Wits School of Mining Engineering, and a network based on custom-created WSN nodes deployed inside the mock mine. Each miner must wear a WSN node, which is small enough to attach to the miner's helmet, for example.

In a normal scenario, such a network enables tracking the movements of the miner. If a portion of the mine collapses and some WSN nodes stop working, the simulation showed that the rest of the nodes can re-establish communication amongst themselves. The demonstration also showed that if the miner node gets buried under a pile of debris, the WSN node can still transmit signals through debris, solid rock, and through mining voids, thus informing the rescuers about the position of the missing miner. These initial results look promising and further research will be conducted in this area.

"In the connected world, there are opportunities that weren't here before. We have something special here that could be used in a mine of the future. It's about finding a person [miner] before the window of opportunity to find them alive closes," says Cawood.